1287642564 has 72 divisors (see below), whose sum is σ = 3509793560. Its totient is φ = 395684352.

The previous prime is 1287642563. The next prime is 1287642589. The reversal of 1287642564 is 4652467821.

1287642564 is a `hidden beast` number, since 1 + 2 + 87 + 6 + 4 + 2 + 564 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 63202500 + 1224440064 = 7950^2 + 34992^2 .

Its product of digits (645120) is a multiple of the sum of its prime divisors (3584).

It is not an unprimeable number, because it can be changed into a prime (1287642563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 527154 + ... + 529590.

Almost surely, 2^1287642564 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1287642564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1754896780).

1287642564 is an abundant number, since it is smaller than the sum of its proper divisors (2222150996).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1287642564 is a wasteful number, since it uses less digits than its factorization.

1287642564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3589 (or 3584 counting only the distinct ones).

The product of its digits is 645120, while the sum is 45.

The square root of 1287642564 is about 35883.7367619372. The cubic root of 1287642564 is about 1087.9237090122.

It can be divided in two parts, 128764 and 2564, that added together give a triangular number (131328 = T₅₁₂).

The spelling of 1287642564 in words is "one billion, two hundred eighty-seven million, six hundred forty-two thousand, five hundred sixty-four".